A boosting system is a device which boosts a target gas to a target pressure.
Here, in recent years, a problem such as global warming due to an increase of emission of carbon dioxide which is known as a greenhouse gas has been evident. Particularly, a large amount of carbon dioxide is included in exhaust gas of a thermal power station, and a technology is known, which boosts gas using a boosting system after the carbon dioxide is separated and recovered, stores the carbon dioxide under the ground on land or under the ground of a sea bottom, and decreases carbon dioxide in the atmosphere.
In this boosting system, carbon dioxide is sequentially compressed by a compressor having multiple stages, the carbon dioxide in which the pressure and the temperature of the carbon dioxide are equal to or greater than a supercritical pressure and a supercritical temperature is cooled by an after-cooler, and the carbon dioxide having a target temperature and pressure suitable for transport and storage can be obtained.
However, in order to obtain the carbon dioxide having the target temperature and pressure in the system including only the compressor which boosts the carbon dioxide to the above-described gas state, an after-cooler having super-high pressure and a large capacity is required, a super-high pressure compression region is generated. Accordingly, operation efficiency or reliability of the entire boosting system decreases.
Here, for example, PTL 1 discloses a boosting system (carbon dioxide liquefied device) in which the above-described after-cooler is not used. In this boosting system, a compressor is provided on a front stage side of the system, a pump is provided on a rear stage side of the system, and compression of carbon dioxide is sequentially performed. In addition, when carbon dioxide is introduced from the compressor into the pump, the carbon dioxide is efficiently liquefied using cold energy of the carbon dioxide which is boosted by the pump and brought into a liquid state of a supercritical pressure.